Chapter 23 Hydrogeology of selected islands of the Federated States of Micronesia

Abstract

This chapter discusses the hydrogeology of selected Islands of the Federated States of Micronesia (FSM). FSM, a new nation in the Pacific, consists of 607 islands spread across more than 2 million km 2 of the western Pacific Ocean within an east-west chain of islands known collectively as the Carolinian archipelago. The FSM was carved from the former Trust Territory of the Pacific Islands, administered by the United States under a U.N. mandate after World War II. The nation comprises four states: Chuuk (formerly Truk), Pohnpei (Ponape), Yap, and Kosrae (Kusaie). The dominant wind direction in the FSM is from the northeast; however, many of the larger storms generate southerly winds. In general, the surficial sediments of the windward islands of Kahlap (Mwoakilloa Atoll) and Falalop (Ulithi Atoll) are coarser than those of the leeward islands of Pingelap (Pingelap Atoll) and Ngatik (Sapwuahfik Atoll). Hydrogeologic reconnaissance studies at Mwoakilloa, Pingelap, Sapwuahfik, and Ulithi Atolls indicate that freshwater lenses are centered on the lagoon side of islands.